As was disclosed in the Japanese Laid-Open Patent Publication No. SHO63-3784 of 1988 for example, in order to store vegetable in fresh condition for a long while in a refrigerator, a method for providing a moisture-sensitive sheet to cover an air-vent of a substantially closed type vegetable container in a refrigerator was proposed.
Structure of this conventional refrigerator cited above is described below.
FIG. 27 is a cross-sectional view of a vegetable storage chamber of the above proposed conventional refrigerator, in which the reference numeral 1 designates the main body of the refrigerator incorporating a freezing chamber (not illustrated) at the top portion, a refrigerating chamber 2 and a vegetable-storage chamber 3 there below.
The reference numeral 4 designates a partition board for partitioning the refrigerating chamber 2 off from the vegetable-storage chamber 3. A pair of air-vents 5 and 6 are provided in the front and rear portions for circulating cooling air therebetween. The reference numeral 7 designates a vegetable storage container which is set inside of the vegetable-storage chamber 3 and has an open upper surface. The vegetable-storage container 7 can optionally be pulled out towards the front while the door 8 is open.
The reference numeral 9 designates a lid which is engageable with and disengageable from the upper surface of the vegetable-storage container 7 to make up a storage container in conjunction with the vegetable-storage container 7. A circular air-vent 10 is provided through the lid 9. In addition, an upwardly folded air-dividing plate 11 is provided at the rear edge of the lid 9.
The reference numeral 12 designates a rectangular moisture-sensitive sheet composed of polyvinyl-alcoholic film for example. As shown in FIG. 28, opposite edges of the moisture-sensitive sheet 12 are secured to bottom surface of the lid 9 with adhesive agent 13 by way of covering the circular air-vent 10. For example, whenever humidity increases beyond 80%, the moisture-sensitive sheet 12 inherently expands and elongates itself, whereas it inherently contracts itself whenever dry condition is generated via decrease of humidity below 80%.
The above-cited conventional refrigerator exerts refrigerating function as described below. After passing through the air-vent 5 of the partitioning board 4, cooled air from the refrigerating chamber 2 is divided by the air-dividing plate 11 and then led to the upper surface of the lid 9 and rear portion of the vegetable-storage container 7.
Then, part of cooled air led to the upper surface of the lid 9 flows into the vegetable-storage container 7 via the air-vent 10 formed through the lid 9, whereas the remaining cooled air and the cooled air passing by the rear surface of the vegetable-storage container 7 respectively return to the refrigerating chamber 2 via the air-vent 6 of the partitioning board 4.
Now, while vegetables are stored under a low temperature cooled by the flow of cooling air described above and whenever the air-vent 10 shown in FIG. 28 remains open, humidity inside of the vegetable-storage container 7 gradually lowers. When humidity lowers below 80%, the moisture-sensitive sheet 12, thus far opening the air-vent 10, contracts itself via drying to adhere to the lid 9 as shown in FIG. 29, thus shutting off the air-vent 10.
On the other hand, while the vegetable-storage container 7 is fully closed, humidity inside of the container 7 increases due to presence of humid vapor emitted via respiratory function of stored vegetables. When humidity exceeds 80%, the moisture-sensitive sheet 12, thus far closing the air-vent 10, gradually expands and elongates itself to open the air-vent 10 again as shown in FIG. 28.
Accordingly, the above-structured refrigerator can prevent the interior of the vegetable-storage container 7 from remaining excessively dry or humid for a long while, thus making it possible to store vegetables for a long while.
Nevertheless, according to the above structure, since the air-vent 10 is opened and closed solely by gradual expansion and elongation and gradual contraction via drying of the moisture-sensitive sheet 12, responsiveness is extremely poor.
In consequence, the above conventional refrigerator cannot fully prevent dewing of the lid 9, via cooled air from the refrigerating chamber 2, due to the delayed prevention of an excessively humid condition in the vegetable-storage container 7 caused by the gradual expansion of the moisture-sensitive sheet 12. Similarly due to the delayed prevention of an excessively dry condition in the vegetable-storage container 7 caused by the gradual contraction of the moisture-sensitive sheet 12, the duration of the flow of cooled air from the refrigerating chamber to the vegetable-storage container 7 is prolonged to cause soft vegetables, such as spinach or the like, to incure dried effect.
In addition, since the moisture-sensitive sheet 12 is composed of expansive material, such as polyvinyl alcholic film for example, not only is its responsiveness extremely poor in testing of its absorption and discharge of moisture, but the moisture-sensitive sheet 12 is also apt to lose its elastic characteristic as a result of repeated absorption and discharge of moisture, causing repeated stretching and contracting of the moisture-sensitive sheet 12.
Consequently, the above-proposed refrigerator cannot maintain humidity inside of the vegetable-storage chamber at an optimal degree for a long while, thus failing to store vegetables in fresh condition for a long while.
Accordingly, an object of the invention is to provide a novel refrigerator which can prevent dewing from occurrence by automatically and precisely controlling humidity inside of the vegetable-storage container and store vegetables in fresh condition for a long while by preserving proper humidity suited for vegetables.